Photographic materials and processes

ABSTRACT

This invention relates to a direct positive light sensitive photographic material comprising non-silver halide physically developable nuclei having adsorbed thereto an organic dye which is an electron acceptor and a process for preparing a positive metallic image comprising physically developing the same.

States Patent [151 3,653,899 Haefner et a1 [4 Apr. 4, 1972 [54]PHOTOGRAPHIC MATERIALS AND 3,250,615 5/ 1966 Van Allan et a1 ..96/88PRUCESSES 2,717,833 9/1955 Wark ..96/64 ,149, 70 91 4 W [72] Inventors:John A. Haefner, Webster; Paul B. Gil- 3 9 96 fayde 96/64 a J R h t b thfN Y 3,314,796 4/1967 Gotze et al ..96/64 es 3,384,485 5/1968 Blake..96/64 [73] Assignee: Eastman Kodak Company, Rochester, 3,109,73611/1963 Sprague et a1. ..96/48 Primary Examiner-William D. Martin 1 12 6[22] F1 ed Nov l9 8 Assistant Examiner-M. Sofocleous 1 PP 775,165Attorney-W. H. J. Kline, J. R. Frederick and Ogden H.

Webster 52 11.8. C1. ..96 48 PD 96 64, 96 88, 1 l 96063 57 ABSTRACT [51]'P 1/62 5/24 This invention relates to a direct positive light sensitivephotolFteldoiSenrch g p material p i g norhsflver halide p y ydevelopable nuclei having adsorbed thereto an organic dye [56]References Cited which is an electron acceptor and a process forpreparing 21 UNITED STATES PATENTS positive metallic image comprisingphysically developing the same. 3,446,619 5/1969 Gilman et al. ...96/633,320,064 5/1967 Hanson et a1. ..96/64 14 Claims, No DrawingsPHOTOGRAPHIC MATERIALS AND PROCESSES This invention relates to lightsensitive photographic materials and processes, and more particularly tophotographic materials and processes which employ physically developablenuclei.

It is known that direct positive images can be obtained by exposingnon-silver halide photosensitive materials comprising physicallydevelopable nuclei associated with a photosensitive substance which, onexposure to actinic radiation, forms a desensitizing agent that rendersthe exposed nuclei inert. A direct positive image is obtained at thenon-exposed nuclei by physical development. For example, Hanson, Jr. etal., U.S. Pat. No. 3,320,064, issued May 16, 1967, describe aphotosensitive composition comprising a light sensitive organic azidecompound, silver nuclei and a thioether photographic coupler. Whenexposed to light, the organic azide reacts with the thioether coupler torelease a composition which deactivates the silver nuclei in exposedareas. On physical development a direct positive image is obtained.While this system has proven quite useful in providing direct positiveimages by physical development, a simpler and more efficient physicaldevelopment system would be desirable.

As noted by Hanson, Jr. et al., in U.S. Pat. No. 3,320,064, it issometimes desirable to employ non-silver halide physically developablenuclei, such as in materials where high image resolution is desired.

It is, accordingly, an object of this invention to provide directpositive light sensitive photographic compositions.

Another object of this invention is to provide photographic elementscomprising direct positive photosensitive compositions.

A further object of this invention is to provide photographic materialsand processes which yield high image resolution.

Still another object of this invention is to provide a novel directpositive photographic physical development process.

Other objects will be apparent from this disclosure and the appendedclaims.

We have now made the important and valuable discovery that novel directpositive light sensitive photographic materials are provided byadsorbing an organic dye which is an electron acceptor onto physicallydevelopable nuclei.

In accordance with one embodiment of this invention, nonsilver halidedirect positive photographic materials are provided which comprisephysically developable nuclei having adsorbed thereto an organic dyewhich is an electron acceptor. On imagewise exposure, such materialsprovide good direct positive images by physical development.

in accordance with another embodiment of this invention, photographicelements are provided comprising a support having coated thereon aphotosensitive material comprising physically developable nuclei havingan electron accepting organic dye adsorbed thereto.

In still another embodiment of this invention, a novel photographicprocess is provided which comprises physically developing an exposedphotographic material comprising physically developable nuclei havingadsorbed thereto an organic dye which is an electron acceptor.

The photographic materials and processes of this invention employphysically developable nuclei. Physically developable nuclei are wellknown in the art, and frequently consist of dispersed particulate matterwhich function as centers for physical development. The term physicallydevelopable nuclei" is a word of art, and refers to materials which areactive sites for the deposition of metal ions, e.g., a metal complexsuch as a silver complex. In the practice of the present invention, theorganic electron accepting dye apparently destroys the ability of thenuclei to promote physical development in just those areas where the dyehas been exposed to actinic radiation.

Any of the physically developable nuclei known to the art can beemployed in the processes and materials of this invention. Suchnucleating agents can consist of particles of any of the heavier metals,such as gold, palladium, platinum and silver, including colloidalsulfides and selenides of the metals of Groups l-B, ll-B, IV-B, VIII ofthe Periodic Table, such as zinc, cadmium, nickel and so forth. Metallicparticles such as titanium particles, for example in the form oftitanium dioxide, palladium particles, and silver particles such asCarey Lea silver particles provide particularly good results in thepractice of the present invention.

The physically developable nuclei typically have an average particlesize in the range up to 0.5 micron and preferably from about 0.001micron to about 0.25 micron. The physical development nuclei inaccordance with the invention can be coated on a support in extremelythin layers. Concentrations of physically developable nuclei of about10" moles per square foot provide highly useful results. Ranges of about0.005 to 10 mg. per square foot, and preferably from about 0.02 to 0.5mg. persquare foot, physically developable nuclei can be used.

The electron accepting organic dyes which are employed in this inventioninclude cyanine, rnerocyanine and benzylidene dyes which contain adesensitizing nucleus; and desensitizing dyes such as pyrylium,thiapyrylium, and selenapyrylium. These dyes when incorporated in a testnegative gelatin silver bromoiodide emulsion, the halide consisting of99.35 mole percent bromide and 0.65 mole percent iodide, at aconcentration of 0.2 millimole of dye per mole of silver halide,desensitize the emulsion more than 0.4 log lE when the test emulsion iscoated on a support, exposed through a step wedge in a sensitometer (toobtain D,,,,,,) to light having a wavelength of 365 nm., processed forthree minutes at 20 C. in Kodak developer D-l9, and is fixed, washed anddried. As used herein the test negative silver bromoiodide emulsions areprepared as follows:

In a container with temperature control is put a solution with thefollowing composition:

(A) Potassium bromide g. Potassium iodide 5 g. Gelatin 65 g. Water L700cc.

And in another container is put a filtered solution consisting of:

(b) Silver nitrate Water 200 g. 2,000 cc.

NMethyl-p-aminophenol sulfate 2.0 g.

Sodium sulfile, desiccated 90.0 g.

Hydroquinone 8.0 g.

Sodium carbonate. monohydrated 52.5 g.

Potassium bromide 5.0 g.

Water to make [.0 liter As noted above, the dyes employed in thisinvention desensitize conventional negative silver halide emulsions.Such emulsions are inherently sensitive to blue radiation. The presentdyes reduce that sensitivity. In addition, these dyes fail to providepractical spectral sensitization for such emulsions. Therefore, it wasquite unexpected to find that they spectrally sensitized photonucleatingcoatings.

The dyes useful herein are electron accepting dyes. They have an anodicpolarographic half-wave potential and a cathodic half-wave polarographicpotential which, when added together algebraically, give a positive sum.As used herein and in the appended claims, polarographic measurementsare made in accordance with the following procedure. Cathodicpolarographic half-wave values are obtained against an aqueoussilver-silver chloride reference electrode for the electrochemicalreduction of the test dye using controlledpotential polarographictechniques. A l X M methanol solution of the test dye is prepared. Thesolvent is 100 percent methanol, if the dye is soluble therein. In someinstances, it is necessary to use mixtures of methanol and anothersolvent, e.g., acetone, to prepare the 1 X 10 M solution of dye. Thereis present in the test solution, as supporting electrolyte, 0.1 Mlithium chloride. Only the most positive (least negative) halfwavepotential value observed is considered, and it is designated herein asE. Voltammetric electropositive (anodic) half-wave values are determinedagainst an aqueous silver-silver chloride reference electrode for theelectrochemical oxidation of the dyes at a pyrolytic graphite electrode,and are obtained by controlled-potential voltammetry using solutionsidentical to those used to determine the cathodic polarographic values.Only the most negative (least positive) halfwave potential observed isutilized, and it is designated herein as E in both measurements, thereference electrode (aqueous silver-silver chloride) is maintained at 20C. Signs are given according to the recommendation of IUPAC at theStockholm Convention, 1953. The well known general principles ofpolarographic measurements are used. See Kolthoff and Lingane,Polarography second edition, Interscience Publishers, New York (1952).The principles of controlledpotential electrochemical instrumentationwhich allows precise measurements in solvents of low conductivity isdescribed by Kelly, Jones and Fisher, Anal. Chem., 31, 1475 (1959). Thetheory of potential sweep voltammetry such as that employed in obtainingthe anodic determinations is described by Delahay, New InstrumentalMethods in Electrochemistry lnterscience Publishers, New York 1954) andNicholson and Shain, Anal. Chem, 36, 706 (1964). Information concerningthe utility and characteristics of the pyrolytic graphite electrode isdescribed by Chuang, Fried and Elving, Anal. Chem, 36, (1964). It shouldbe noted that the spectral sensitizing dyes operable in this inventioninclude those dyes which contain oxidizable ions, such as iodide. Forexample, many dyes which are iodide salts are useful herein. However,the polarographic measurements referred to above cannot be determined inthe presence of oxidizable ions. Therefore, such dyes are converted,just for purposes of making polarographic determinations, to an anionsuch as chloride or p-toluenesulfonate, which do not interfere in makingaccurate polarographic measurements. Hence, dyes containing oxidizableions are included within the scope of the useful dyes defined herein andin the appended claims.

As noted above, this invention is applicable to spectral sensitizationof photonuclear coatings or layers with certain cyanine, merocyanine,benzylidene and pyrylium type dyes which also function as electronacceptors. The term cyanine dye, as used herein, is to be construedbroadly as inclusive of simple cyanines, carbocyanines, dicarbocyanines,tricarbocyanines, etc. containing a desensitizing nucleus. The termincludes symmetrical nd unsymmetrical cyanine dyes, as well aschain-methine-substituted dyes. Also included are the reaction productsof bromine and certain simple cyanine sensitizing dyes. Cyanine dyesuseful herein feature the amidiniumion chromophoric system. See Mees andJames, The Theory of the Photographic Process published by the MacMillanCompany (1966) page 201. The term merocyanine is also used broadly, andincludes dyes which are characterized by the amidic chromophoric system.See Mees and James, supra, pages 201 and 218. The term pyrylium type"dye in the above text refers broadly to pyrylium salts, thiapyryliumsalts and selenapyrylium salts.

As used herein and in the appended claims, desensitizing nucleus refersto those nuclei which, when converted to a symmetrical cyanine dye andadded to a gelatin silver chlorobromide emulsion containing 40 molepercent chloride and 60 mole percent bromide, at a concentration of fromabout 0.01 to 0.2 g. dye per mole of silver, cause at least an percentloss in the blue speed of the test emulsion when it is sensitometricallyexposed and developed three minutes at 20 C. in Kodak developer D-l9,the composition of which is given above. Preferably, the desensitizingnuclei are those which, when converted to a symmetrical carbocyanine dyeand tested as described above, essentially completely desensitize thetest emulsion to blue radiation. Substantially complete desensitization,as used herein, results in at least a percent, and preferably a percentloss of speed to blue radiation. Desensitizing nuclei which areespecially effective herein include 5- to 6-membered nitrogen containingheterocyclic nuclei of the type used in cyanine dyes having a nitrosubstituent; imidaZo[4,5-b]quinoxaline nuclei; and 2-aromaticallysubstituted indole nuclei. Other desensitizing nuclei arev the nitrosubstituted aryl nuclei used in the benzylidene type dyes of thisinvention.

One highly useful class of dyes which may be used in this inventionincludes cyanine and merocyanine dyes which contain the desensitizingimidazo[4,5-b1quinoxaline nucleus. Typical useful cyanine dye salts ofthis class comprise two nuclei joined together by methine linkage, oneof the nuclei being an imidazo[4,5-b]quinoxaline nucleus which is joinedthrough the Z-carbon atom thereof to the methine linkage, and a secondnucleus to complete the cyanine dye. Advantageously, the second nucleusof such dyes contains a heterocyclic nitrogen atom and the methinelinkage is part of a polyene chain containing an equal number ofalternating single and double bonds, one terminal carbon atom of thepolyene chain being the 2-carbon atom of an imidazo[4,5 b]quinoxalinenucleus, the other terminal carbon atom of the polyene chain being inthe second nucleus and attached to a heterocyclic nitrogen atom.Preferably, the second nucleus in these dyes is also a desensitizingnucleus.

Also useful herein are merocyanine dyes comprising two nuclei joinedtogether through an acyclic methine group which is part of a polyenechain containing an equal number of alternating single and double bonds,one of the terminal atoms of the polyene chain being the 2-carbon atomof an imidazo-[4,5-b]quinoxaline nucleus, the other terminal carbon atomof the polyene chain being in a heterocyclic ring of a second nucleusand attached to an extracyclic carbonylic oxygen atom.

Also useful herein are cyanine dyes comprising twoimidazo[4,5-b1quinoxaline nuclei joined together through a polyene chaincontaining an equal number of alternating single and double bonds, theterminal carbon atoms of the polyene chain being the 2-carbon atoms,respectively, of the imidazo-[4,5-b]quinoxaline nuclei. Preferably, thepolyene chain of these dyes is composed of five carbon atoms.

Preferred classes of dyes featuring an imidazo[4,5-b1-quinoxalinenucleus include those represented by the following general formulas:

imidazolidinedione, etc.); a 2-imidazolin-5-one nucleus (e.g.,2-propylmercapto-2-imidazolin-5-one, etc.), etc. Especially useful arenuclei wherein represents the atoms required to complete a heterocyclicnucleus containing atoms in the heterocyclic ring, 3 of said atoms beingcarbon atoms, 1 of 5 IV. R

wherein R, R, and X are as previously defined and R representsa memberselected from an alkyl group of from 1-4 carbon atoms, e.g., methyl,ethyl, propyl, isopropyl, butyl, secbutyl, etc., or benzyl, phenylethyl.In general, such dyes are produced by heating a mixture of a quaternarysalt of above Formula IV with the appropriate intermediate. The reactionmixtures are heated to advantage in any of the suitable solvents used indye synthesis including solvents such as ethanol, propanol, dioxane,pyridine, quinoline, and the like, at temperatures up to the refluxtemperature of the mixture. Advantageously, the reaction is carried outin the presence of a basic condensing agent such as a pyridine or atertiary amine, e.g., trimethylamine, triethylamine, tri-n-propylamine,tri-nbutylamine, N-methylpiperidine, N-ethylpiperidine, N,N,-dimethylaniline, N,N-diethylaniline, etc.

The symmetrical cyanine dyes of Formula I are prepared to advantage byheating a mixture of a compound of Formula IV (in which R is methyl)with diethoxymethyl acetate (forms carbocyanine), trimethoxypropene(forms dicarbocyanine), l-anilino-5-phenylimino-l ,3-pentadienehydrochloride (forms tricarbocyanine), etc., preferably in a solvent andin the presence of a basic condensing agent such as mentioned above, ifdesired.

The unsymmetrical cyanine dyes of Formula II are prepared advantageouslyby heating a mixture of a compound of Formula IV (in which R is methyl)with a compound of the formula:

i i 7 "A 7 CR7 wherein R L, X and Z are as previously defined, g and qeach represents a positive integer of from 1 to 2, R represents an arylgroup of from 67 carbon atoms, e. g., phenyl, p-tolyl, etc., and Rrepresents an alkyl group of from 1-12 carbon atoms. This is preferablycarried out in a suitable solvent and in the presence of a basiccondensing agent.

Merocyanine dyes, such as those of Formula III, are made to advantage byheating a mixture of a compound of Formula IV (in which R is methyl)with a compound of the formula:

wherein Q is as defined previously and W represents the group wherein prepresents a positive integer of from 1 to 2 and L, R, and R are aspreviously defined.

Typical specific useful dyes containing the imidazo-[4,5-b]quinoxalinium nucleus include 1,1,3,3-tetraethylimidazo-[4,5-b]quinoxalinocarbocyanine chloride; l,1',3 ,3tetraethyl-imidazo[4,5-b]quinoxalinodicarbocyanine chloride;l,3,3'-triethylimidazo[4,5-b]quinoxalinooxacarbocyanine iodide; 1,3 ,3'-triethylimidazo 4,5-b lquinoxalinothiacarbocyanine iodide;1,3-diethyl-1 ',3 ,3- trimethylimidazo[4,5-b]quinoxalinoindocarbocyanineiodide; l,3-diethyl-3'-methylimidazo[4.5-bl-quinoxalinothiazolinocarbocyanine iodide; 1 ,l ',3-triethylimidazo[4,5-b]quinoxalino-2-carbocyanine iodide; 5-[( 1,3-diethylimidazo[4,5-b]quinoxalin-2-ylidene)-ethylidene]-3-ethylrhodanine; 5-[( 1,3-diethylimidazo[4,5-b1quinoxalin-2- ylidene)ethylidenel-l ,3-diethyl-2-thiobarbituric acid; 1,1,3 ,3'-tetra(2-hydroxy-ethyl)imidazo[4,S-blquinoxalinocarbocyanine iodide;l.3-di(2-hydroxyetl1yl)l .3 .3-trimethylimidazo[4.5-b]quinoxalinoindocarbocyanine iodide:

l ,1,3.3-tetraallylimidazo[4.5-b]-quinoxalinocarbocyaninep-toluenesulfonate;l,3-diallyl-3'-ethylimidazo[4,5-b]quinoxalinooxacarbocyanine iodide;1,3-diallyl-3-ethylimidazo[4,5- b]quinoxalinothiacarbocyanine iodide;1,3-diallyll ,3 ,3 trimethylimidazo[4,5-b]quinoxalinoindocarbocyanineiodide;I,3-diallyl-3-ethyl-4.5-benzoimidazo-[4,5-bJquinoxalinothiacarbocyaninep-toluenesulfonate; 1,3-diallyl-lethylimidazo[4,5b]quinoxalino-2-carbocyanine iodide; 5-[(1,3-diallylimidazo[4,5-b]quinoxalin-2(3l-I)-ylidene)-ethylidene]-3-ethylrhodanine;l,1',3 ,3 -tetraphenylimidazo[4,5- b]-quinoxalinocarbocyaninep--toluenesulfonate; 3 '-ethyl1,3-diphenylimida2o[4,5]quinoxalinothiacyanine iodide; 3- ethyll,3-diphenylimidazo[4,5-b]quinoxalinooxacarbocyanine iodide;3'-ethyl-1,3-diphenylimidazo[4,5 -b]quinoxalinothiacarbocyanine iodide;1 ,3',3'-t rimethyl-1,3-diphenylimidazo[4,5-b]quinoxalinoindocarbocyanine iodide;lethyl-1,3-diphenylimidazo[4,5-b]-quinoxalino-2'-carbocyanine iodide;5-[(1,3-diphenylimidazo-[4,5-b]quinoxalin- 2(3H)-ylidene)ethylidene]-3-ethylrhodanine, 6-chloro-2-[( I-methyl-2-phenyl-3-indolyl)vinyl]-1,3-diphenylimidazo[4,5-b]quinoxalinium p-toluenesulfonate, 6,6 '-dinitrol ,1 ,3 ,3tetraphenylimidazo[4,5-b]quinoxalino p-toluenesulfonate, and 9-[2-(1-methyl-2-phenyl-3-indolyl)vinyl]-8, l O-diphenyl-8H-benzo[f]imidazo[4,5-b]quinoxalinium bromide.

A more detailed description for the preparation of dyes of the typedescribed above is contained in Brooker and Van Lare Belgian Pat. No.660,253, issued Mar. 15, 1965, and Brooker and Van Lare Belgian Pat. No.695,368 granted Sept. 11, 1967, and U.S. Application Ser. No. 609,791filed Jan. 17, 1967, which is a continuation-in-part of Brooker andVanLare U.S. Application Ser. No. 573,183, filed Aug. 18, 1966, andBrooker and Van Lare U.S. Application Ser. No. 286,469, filed June 10,1963.

It will be noted that in the dyes described above, theimidazo[4,5-b]quinoxaline nucleus can be substituted, for example, withhalogen (such as monoor dichloro, monoor dibromo) nitro, or with a fusedring.

Another class of dyes which may be used in accordance with the inventionto spectrally sensitize organic photoconductors are cyanine dyes whichfeature a 2-aromatically substituted indole nucleus attached to themethine chain of the cyanine dye by the 3-carbon atom of the indolenucleus. Dyes of this type are described by Coenen et al. U.S. Pat. No.2,930,694 issued Mar. 29, 1960; British Pat. No. 970,601 and Litzermanet al. Belgian Pat. No. 695,365 granted Sept. 11, 1967, and U.S. Pat.application Ser. No. 609,764, filed Jan. 17, 1967. These dyes includetrimethine cyanine dyes which feature two 2-aromatically substitutedindole nuclei each joined by the 3-carbon atom thereof to the respectiveterminal carbon atoms of the trimethine chain. Such dyes include, forexample, bis( 1-methyl-2-phenyl-indole-3 )-trimethine cyanine bromide.Also useful are unsymmetrical dyes having first and second nuclei joinedby methine linkage, one nucleus being a 2-aromatically substitutedindole nucleus, and the second nucleus being a heterocyclic nucleus tocomplete the dye. The indole nucleus of such dyes is attached to themethine chain of the dye through the 3-carbon atom of the inwherein Drepresents a 2-aromatically substituted indole nucleus attached to themethine chain through the 3-carbon atom of the indole nucleus; Lrepresents a methine linkage; and, Y represents a desensitizing nucleus.For example, a preferred desensitizing nucleus is animidazo[4,5-b]quinoxaline nucleus attached, through the 2-carbon atomthereof, to the methine chain. Spectral sensitizing dyes of this typecan be prepared using any of the methods generally used for preparingsuch dyes. One convenient method involves refluxing, in a suitablesolvent, a carboxaldehyde derivative of a 2-aromatically substitutedindole with an alkyl substituted quaternary salt of a compoundcontaining the desired desensitizing nuclei. For example, a2-aromatically substituted indole-3-carboxaldehyde can be refluxed in asolvent such as acetic anhydride with a2-alkylimidazo[4,5-b1quinoxalinium salt or a 2-alkylenepyrrolo-[2,3-b]pyridine compound to provide the desired dye. Thesubstituent in the 2-position of the indole nucleus may be any suitablearomatic group, such as a phenyl nucleus, which can contain variousgroups such as alkyl (e.g., methyl, ethyl, propyl, butyl, etc.) alkoxy(e.g., methoxy, ethoxy, propoxy, butoxy, etc.) halogens such as bromine,fluorine, or chlorine, as well as aryl such as naphthyl or phenyl. Amongthe useful dyes of this class are those having the following formula:

wherein L represents a methine group and R and R each represents a valueselected from those given for R above; Z is selected from the valuesgiven for Z above; p represents an integer of from 1 to 2; and, Arrepresents an aromatic substituent such as phenyl or those referred toabove. Some specific useful dyes of this class include:

1,Bqliethyl-l-methyl-2-phenylirnidaz0l4,5-b]quinoxalin0-3-indolocarbocynnine iodidefich1oro-1"methyl-1,2,3-triphenylimidazo[4,5-b]quinoxallno-3indolocarbocyanine p-toluenesulionate Mr-v3ethyll-methyl-ZmhenyHY-nitro-Zi-indolothiacnrhocyaninc iodide5-cliloro-1 ,3-din1cth yl-Zphcnyl45'-nitro-3-indolothiacarbocyaninup-tolucnusulfonate Still another class of useful dyes in accordance withthis invention are the cyanine and merocyanine dyes in which at leastone nucleus, and preferably two nuclei thereof, contains a desensitizingsubstituent such as nitro. Such, dyes of the cyanine salt type (FormulaIX below) comprise first and second 5- to -membered nitrogen containingheterocyclic nuclei of the type used in cyanine dyes joined together bymethine linkage at the 2-carbon atoms thereof, at least one of saidnuclei being substituted by a nitro group. The merocyanine dyes (FormulaX below) comprise first and second 5- to G-membered nitrogen containingheterocyclic nuclei joined together by methine linkage; the first ofsaid nuclei being a ketomethylene nucleus of the type used inmerocyanine'dyes joined at a carbon atom thereof to said linkage; andsaid second nucleus being of the type used in cyanine dyes having anitro substituent thereon and joined at a carbon atom thereof to saidlinkage, to complete said dye. Typical dyes of this class arerepresented by the formulas:

wherein R R R each is independently selected from a value given for Rabove; Z Z and Z each represents a value given for Z above; at least oneof 2;, and Z and at least one of Z and Q contains a nitro group; Q has avalue given for Q above; 3, j and h each represents a positive integerof from 1 to 2, k represents a positive integer of from 1 to 3; Xrepresents an acid anion; and, L represents a methine group. A typicaldye of this class is 3,3'-diethyl-6,6-dinitrothiacarbocyanine salt.

Another useful class of dyes which can be employed in the practice ofthis invention are the cyanine dyes which feature a trifluoromethylgroup either in the nucleus or the chain. Representative dyes of thisclass can be represented by Formula IX above wherein an L grouprepresents the substituent:

The most useful dyes of this class are those wherein a hydrogen atom inthe methine chain of the cyanine dye is replaced with a trifluoromethylgroup. The cyanine dye can be a simple cyanine, a dicarbocyanine or atricarbocyanine. Expecially useful dyes are the meso-trifluoromethylsubstituted carbocyanines. Dyes of this class preferably contain anucleus such as those derived from benzimidazole, benzoxazole,benzothiazole, benzoselenazole or indole.

Also useful herein are the benzylidene dyes in which one nucleus is aketomethylene nucleus of the type used in merocyanine dyes joined by amethine group to a nitro substituted aryl nucleus. Typical dyes of thisclass are represented by the formula:

wherein L represents a methine group; O has the previously definedvalue; and Ar represents a nitro substituted aryl group, e.g.,m-nitrophenyl, p-nitrophenyl, a nitronaphthyl, etc.

Another useful class of dyes which can be employed in this invention arethe electron accepting cyanine dyes having at least one methine groupwherein the hydrogen atom thereof is replaced with a chlorine, bromineor iodine atom, such as the dyes described in Belgian Pat. No. 695,354of Sept. 1 l, 1967, and Gilman et al. US. Pat. Application Ser. No.607,734 filed Jan. 17, 1967. Best results are obtained with themonomethine cyanine dyes, such as the reaction product of bromine with al,l'-diethyl-2,2-cyanine dye salt or a l',3-diethylthia-2- cyanine dyesalt.

Still another class of dyes useful in the practice of this inventioninclude pyrylium, thiapyrylium and selenapyrylium compounds and moreparticularly those represented by the following formula:

wherein A represents an oxygen, sulfur or selenium atom, X represents anacid anion which has no adverse effects on the emulsion, e.g., chloride,bromide, iodide, thiocyanate, sulfamate, perchlorate,p-toluenesulfonate, methyl sulfate, ethyl sulfate, fluoroborate,sulfoacetate, borofluoride, trifluoroacetate, etc., and R, R", and R'each represents an alkyl group including substituted alkyl (preferably alower alkyl containing from 1-4 carbon atoms), e.g., methyl, ethyl,propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, benzyl,phenethyl, a styryl group such as styryl, o-, pand mmethoxy-styryl, pandm-styrylstyryl, N-phenylacridanylidenemethyl groups, etc., etc.; analkoxy group, preferably a lower alkoxy, e.g., methoxy, ethoxy, propoxy,isopropoxy, butoxy, etc.; an aryl group (including substituted aryl),e.g., phenyl, o-, pand m-toly, o-, pand m-ethylphenyl, etc., analkoxyphenyl group, e.g., o-, pand m-anisyl, o-, p, and methoxyphenyl,etc., a hydroxyalkoxyphenyl group such as B- hydroxyethoxyphenyl,w-hydroxyamyloxyphenyLw-hydroxybutoxyphenyl, etc., a carboxyalkoxyphenylgroup such as carboxymethoxyphenyl, B-carboxyethoxyphenyl, (o-carboxybutoxyphenyl, etc., a biphenyl group, an azidophenyl such as o-,pand m-azidophenyl, etc., an acylamidophenyl group such as o-, pandm-acetamidophenyl, p-propionamidophenyl, etc., an alkoxycarbonylphenylgroup such as methoxycarbonylphenyl, w-butoxycarbonylphenyl,chloromethoxycarbonylphenyl, bromomethoxycarbonylphenyl, etc., anaphthyl group such as lor Z-naphthyl; etc., an arylalkenyl grouptypically having 1-20 carbon atoms such as 4-phenylbutadienyl,3-methyl-4-phenylbutadientyl, etc., and the like. The dye compoundswherein R, R" and R each represents an aryl group are especiallyefficacious in this invention and are the preferred species of thisclass of dyes.

Typical dyes coming under the definition of Formula Xll above include;for example, 2,-di-p-methoxyphenyl-4-phenylpyrylium fluoroborate;2,6-bis-(p-anisyl)-4-(p-n-amyloxyphenyl)pyrylium perchlorate;2-(p-n-amyloxyphenyl) 4,6- diphenylpyrylium fluoroborate;

2-(4-Phenylbutadienyl)- 4,6-diphenylpyrylium perchlorate6-(4-Phenylbutadienyl)- 2,4-diphenylthiapyrylium perchlorate2,6-Bis-(p-ethylphenyl)- 4-(p-anisyl)pyrylium perchlorate2,6-Bis-(p-ethylphenyl)- 4-( p-anisyl)thiapyrylium perchlorate2,6-Diphenyl-4-(p-anisyl)- thiapyrylium chloride2,6-Bis-(p-ethylphenyl)- 4-(p-n-amyloxyphenyl) pyrylium fluoroborate2,6-Bis-(p-anisyl)-4- (p-n-amyloxyphenyl) thiapyrylium perchlorate2,4-Diphenyl-6-styrylpyrylium perchlorate 2,6-Bis-(p-anisyl)-4-phenylthiapyrylium fluoroborate2,6-Bis-(p-ethylphenyl)-4-(p-n-amyloxyphenyl)pyrylium perchlorate2,4,6-Tris(p-anisyl)pyrylium fluoroborate 2-[p-(B-hydroxyethoxy)phenyl]-4,6-diphenylpyrylium perchlorate 2,4,-Triphenylselenapyryliumfluoroborate 2,4,6-Tris-(p-anisyl)thiapyrylium p-toluenesulfonate2,4,6-Tris-(p-anisyl)thiapyrylium sulfoacetate2,6-Bis-(p-chloromethoxycarbonylphenyl)-4-phenylpyrylifluoroborate2,6-Bis-(p-ethylphenyl)-4- (p-n-amyloxyphenyl)thiapyrylium fluoroborate2,4,6-Tris(p-anisyl)pyrylium perchlorate2,4,6-Tris-(p-anisyl)thiapyrylium perchlorate2,6-Diphenyl-4-(p-acetaminophenyl)pyrylium perchlorate2-[p-(B-hydroxyethoxy)- anisyl)pyrylium perchlorate 2-( Z-naphthyl)-4,6-diphenyl thiapyrylium perchlorate 2,4,6-Tris-( p-anisyl)thiapyrylium trifluoroacetate 2-Methyl-4,6-bis-(p-anisyl)2,6-Bis-(p-anisyl)-4-(p-nfluoroborate; and the like.

The organic electron accepting dyes can be adsorbed onto the physicallydevelopable nuclei in any convenient manner. For example, a dispersioncan be formed of the physically developable nuclei in a suitablehydrophilic colloid, the organic dye can be mixed therewith and theresulting composition can be coated onto a suitable support and dried.If desired, a dispersion of physically developable nuclei can bedispersed in a hydrophilic colloid and coated on a suitable support andthe resulting coating can be dipped in a suitable solution of the dye,or a solution of the dye can be swabbed, brushed or sprayed over thecoating. When binderless vacuum amyloxyphenyl thiapyrylium depositedcoatings of physically developable nuclei are utilized, it is convenientto dip the support having the physical developable nuclei thereon into asuitable solution of the dye, or by swabbing, brushing or spraying thedye solution onto the binderless coating of physically developablenuclei.

The term physical developer is used herein as a word of art. It refersto materials which contain a source of reducible metal and a reducingagent which causes the reducible metal to be deposited on a particularsite.

Physical development may be conducted in accordance with the practice ofthis invention with any suitable metal. Silver is highly useful inpreparing images in the physical development process. However, othermetals are known for use in physical development and can be used inplace of silver. Metals which are members of electromotive scale belowhydrogen are used most commonly for physical development and theyinclude copper, arsenic, antimony, platinum, gold, mercury, silver andthe like.

Various physical development processes can be utilized. For example, animagewise exposed element can be contacted with the emulsion side of aconventional negative photographic silver halide emulsion previouslywetted with a conventional photographic developer modified by theinclusion therein of a silver halide solvent, such as sodiumthiosulfate. After contacting for a brief time, the two layers areseparated and a positive silver image is produced in the unexposedregions of the layer containing the physically developable nuclei.Exposed regions of the layer are essentially free from any silver image.

In another physical development technique, the exposed materialcomprising physically developable nuclei is immersed in a physicaldeveloper solution comprising silver halide, a conventional silverhalide developing agent, and silver halide solvent. At the time requiredto obtain sufficient density, usually several minutes, the element isremoved to obtain a direct positive silver image.

The binder for the above photonucleating coating compositions is notcritical since practically any water permeable colloid known for use insilver halide photography can be used such as gelatin,carboxymethylcellulose, zein, albumin, various synthetic resins such aspolyvinyl alcohol, polyvinyl pyrrolidone, acrylic resins, and the like.Although the concentration of the binder can vary over a wide range, ithas been found that quite useful coating compositions are preparedwherein the binder is present in the range up to about percent by weightof the total coating melt.

The wet thickness of the coatings can be in the range of about from0.001 to about 0.01-inch with a preferred wet thickness in the rangefrom about 0.003 to about 0.006-inch. Thicker coatings can also beemployed without detracting from the invention.

Suitable support materials for preparing the light sensitivephotographic elements of the invention include cellulose acetate,cellulose acetate propionate, cellulose nitrate, polyethylene,polypropylene, polystyrene, polyvinyl chloride, polyethyleneterephthalate, paper, metal, glass, and the like.

When diffusion transfer physical development is employed, any of theknown silver halide emulsions may be used in contact with the lightsensitive, exposed, silver-dye complex emulsion, such as silverchlorobromide, silver chloroiodide, silver chlorobromoiodide, silverbromide, and silver bromoiodide.

In developing the exposed layers of the invention any of the usualdeveloping agents can be used in the developer compositions such asN-monomethyl-p-aminophenol sulfate; dihydroxybenzene; hydroquinone,p-phenylenediamine developers; hydroquinone compounds (e.g.,chlorohydroquinone, dichlorohydroquinone, bromohydroquinone, etc.); 1-phenyl-3-pyrazolidone and its derivatives; triaminophenols; and thelike.

Silver halide solvents for use in the physical developing process of theinvention include alkali metal thiosulfates, ammonium thiosulfate,alkali metal thiocyanate, ammonium thiocyanate, sodium sulfite, etc.

The following examples are included for a further understanding of theinvention.

EXAMPLE I A direct positive silver image is formed in a diffusiontransfer physically developable system as follows:

A photonucleating coating is prepared as follows: To ml. of 5 percentgelatin add:

a. 4 ml. of 7 /5 percent saponin solution b. 3 ml. of 10 percentformaldehyde solution To 10 ml. of the above solution is added 0.10 ml.of 0.10

Molar silver nitrate solution.

Coatings of above dispersion having a 0.004-inch wet thickness are madeon a cellulose triacetate film support to give a coverage ofapproximately 2.6 mg. Ag N0 per square foot, 400 mg. of gelatin persquare foot, and 0.065 mg. of dye per square foot.

A step tablet exposure is given by exposing the coating 15 seconds to aIOO-watt Tungsten lamp at a distance of 3 feet. The coating is thenimmersed for 2 minutes in a solution of the dye-l,l'-diethyl-2,2-cyaninesulfate which had been reacted with bromine-pyrrolidone complex toproduce a light sensitive blue colored solution. The dyed coating isthen dried and given a stepped exposure perpendicular to the firstexposure and processed by contacting with an unexposed fine grain silverchlorobromide film previously soaked for 3 seconds in a developersolution of the composition:

Developer l Methylarninoethanol-sulfur dioxide The wet fine grain silverchlorobromide film is rolled in contact with the dyed and re-exposedcoating. After 2 minutes contact(at about 20)the two layers are peeledapart. The second exposure removed the effect of the first exposure in amanner proportional to the intensity of the second exposure.

The above process is repeated except that a line image is employed in aprior stepwedge exposure. Good reversal line images are obtained.

By giving the photonucleating coating a uniform fogging exposure of 4seconds to a l00-watt lamp at a distance of 3 feet and then immersingthe layer in the blue dye solution, it is found that a second imageexposure produces a high density direct positive line image after usingthe diffusion transfer physical development described above. The qualityof the reversed silver image is excellent.

PREPARATION OF DYE SOLUTION To 40 ml. of solution of ethyl alcoholcontaining 5 X 10 grams of the sensitizing dye,l,l'-diethyl-2,2'-cyanine sulfate, is added 20 ml. of an aqueoussolution containing 2 X 10" grams of a bromine-pyrrolidone complex soldby the General Aniline and Film Corp.

The mixture of the above two solutions results in the conversion of thepreviously red colored solution of the dye (absorption max 540 ,u.) to ablue colored solution (absorption max 590 u). The blue form of the dyeis light-sensitive and should be prepared and used only in totaldarkness to prevent spontaneous decomposition.

EXAMPLE 2 The process of above Example 1 is repeated, except that thedye solution in this instance is the reaction product of l, 3-diethylthia-2-cyanine iodide and bromine-pyrrolidone complex. Theresults are generally similar to those of Example 1, e.g., a highdensity direct positive line image of excellent quality is likewiseobtained.

EXAMPLE 3 This example illustrates the production of a direct positivesilver image by preforming metallic nuclei latent images in a titaniumdioxide layer and incorporating an electron acceptor such as abrominated dye into the system, followed by exposure and development ina solution physical developer. The following coating was prepared in thelight.

A dispersion of finely divided titanium dioxide in 50 ml. of water isstirred with 50 ml. of 10 percent gelatin solution at 40 C. To 10 ml. ofthe dispersion is added 0.1 ml. of 0.1 N Ag N ml. of water and 0.3 ml.of percent formaldehyde solution and a coating made at 0.002 in. wetthickness on polyethylene-coated paper. A metallic nuclei latent imageis formed in the titanium dioxide by the action of light in preparingthe coating.

The above prepared coating layer comprised:

Silver (AgNO;,) 3 mgjsquare foot Gelatin 150 mg./square foot TiO, 300mg./square foot The coated paper is then dipped in a brominated dyeunder red safelights, the brominated dye being prepared by adding 98 mg.of N-bromosuccinimide in 50 ml. of methanol to 100 mg.1,1'-diethyl-2,2-cyanine chloride in 50 ml. of methanol. The dyed lightsensitive element is then dried in the dark, exposed for 5-l0 seconds toa photoflood lamp through a negative line image and immersed directlyfor 2 minutes in a physical developer solution C.) of the followingcomposition:

For use:

Mix parts A and B 1:1

For making silver chloride:

l)42.4 g. AgNO in 900 cc. of water 2) 42.4 g. KCl in 900 cc. of water 3)Mix 90 cc. of( l and 90 cc. of(2) in a 6 ounce bottle 4) Let standovernight, then pour otT liquid for use Each bottle contains 2.5Xl0 '2moles. therefore, two bottles are required to make 5X l 0' molar octylphenoxy ethoxy ethyl dimethyl-p-chlorobenzyl ammonium chloride Afterdevelopment, the element is rinsed in water. A direct positive silverimage is obtained with the image appearing after 20 seconds in thedeveloper. It was clear and sharp. The titanium dioxide in the aboveprocedure can be replaced with zinc oxide to give a generally similardirect positive silver image.

EXAMPLE 4 In this example, the sensitizing dye is incorporated into thenuclei containing composition and the mixture coated onto a suitablesupport material. This element is then exposed and developed to apositive image by solution physical development. All operations arecarried out under red safelights.

To 15.0 of finely divided titanium dioxide dispersed in 200 ml. of waterin a 40 C. bath is added 150 ml. of 10 percent gelatin and 30 ml. of 1.0percent silver nitrate. The The pH is adjusted to 9.0, the temperatureraised to 55 C. and 6.0 ml. of 5 percent formaldehyde solution is added.The stirred mixture is held 16 minutes at 55 C. after which the pH islowered to 5.8. A 20 ml. aliquot of this melt is mixed with 13 ml. ofbrominated dye solution, (same as that described in above Example 3) andthe mixture is coated at 4.7 ml./ft. on polyethylene-coated paper togive a coverage of 1.6 mg./ft. of silver, 2.7 mg./ft. of dye (as thedibromide) and mg./ft. of titanium dioxide.

A sample of the above prepared dyed light sensitive element is given aspectrograph exposure of 2 minutes at a slit width of 10 mm. on amonochrometer and then developed 2 minutes in Developer 2 (compositionof which is shown in Example 3 herein) at room temperature. Excellentdirect positive spectral response is shown.

EXAMPLE 5 This example is generally similar to that of preceding Example4, except that the titanium dioxide is omitted. All operations in thisexample are carried out under red safelights.

A dispersion is prepared with 30 ml. of aqueous 1.0 percent silvernitrate and 350 ml. of aqueous 4.3 percent gelatin in a 40 C. bath. Themelt temperature of this dispersion is raised from 40 C. to 55 C. at arate of 1.7 C. per minute and then held 2 minutes at 55 C. beforelowering the pH to 4.75, and lowering the temperature to 40 C. A 20 ml.aliquot of this melt is mixed with 13 ml. of the brominated dye solutiondescribed in above Example 3 and the mixture is coated 4.7 ml. persquare foot on polyethylene coated paper to give a coverage of L6 mg. ofsilver per square foot and 2.7 mg. per square foot of the brominateddye.

A sample of the above prepared light sensitive element is given aspectrograph exposure of 2 minutes at a slit width of 10 mm. on amonochrometer and then developed in Developer 2 (composition of which isgiven in above Example 3) at room temperature. An excellent directpositive spectral response is obtained.

EXAMPLE 6 This example illustrates the use of evaporated silver nucleiphysical development sites.

Under red safelights a sample containing 0.15 mg. per square foot, ofparticle size 20 A. or less, of evaporated silver on polyethylene paperis immersed in .the previously described brominated dye solution ofabove Example 3 and then drained and dried. The sample (in contact witha line negative) is given a 30-second photoflood exposure at a distanceof 1 foot and then developed for 3 minutes in Developer 2 (compositionof which is given in above Example 3) at room temperature. An excellentdirect positive image is obtained.

EXAMPLE 7 By the same procedure (Example 6 above) a direct positiveevaporated palladium in place of evaporated silver. The coating coveragein this example is approximately 0.15 mg. of palladium per square foothaving an average particle diameter size of about 20 A. or less.

EXAMPLE 8 The procedure of above Example 7 is repeated, except that acoating of palladium nuclei, prepared by-reducing palladium chloratewith hypophosphite, in a terpolymer of acrylic acid, acrylonitrile andvinylidene chloride in gelatin (25 percent of monomer in gelatin) isapplied on a polyethylene-coated paper using a 4-minute photofloodexposure at a distance of 6 inches, followed by developing(at 20 C.) inDeveloper 2 (composition of which is given in above Example 3 for 1minute. An excellent direct positive image is obtained. The coatingcoverage in that example is approximately 0.04 mg. palladium per squarefoot of average particle diameter size of about 50 A. or less.

In place of the brominated dye solution employed in above Examples 4 to9, there can be substituted a like amount of a solution of other dyessuch as, for example, S-m-nitrobenzylidene rhodanine;1,3-diethyl-l'-methyl-2'-phenylimidazo[4,5-b]quinoxolino-3-indolocarbocyanine iodide;3-ethyl-lmethyl-2-phenyl6'-nitro-3-indolothiacarbocyanine iodide; andthe like. It will be understood that the above carbocyanine dyes can beused in any of the mentioned salt forms, e.g., the chloride, bromide,perchlorate, p-toluenesulfonate, etc. salts, which likewise functioneffectively as electron acceptors and spectral sensitizers in thesystems of the above examples. It will also be understood that thenuclei can be combined with the electron accepting dye either by mixingsolutions of the two and coating them or by coating the nuclei alone andthen imbibing the dye.

EXAMPLE 9 In this example a pyrylium type dye such as defined in FormulaVIII above is employed as an electron acceptor and spectral sensitizerfor preparing a Carey Lea Silver (CLS) for diffusion transfer physicaldevelopment. I

Colloidal silver having an average diameter of from 50 to 70 A. isprepared by a modified CLS technique (M. Carey Lea, Kall. Zeitschrift,13, 180 1913).

A gelatin coating of above CLS is prepared. This is applied over agelatin pad (which contains 475 mg. of gelatin per square foot) in suchthickness as to give a coverage of 25 mg. of gel and approximately 0.4mg. of silver per square foot.

The above CLS coating is sensitized by bathing it for 30 seconds in asolution which contains 0.1 g. per liter of the thiapyrylium dye.

2, 6-bis(p-methoxyphenyly t-(pentyloxyphenyl) thiapyrylium perchlorateThe dye is dissolved in a I percent potassium bromide solution with thesolvent composed of equal parts of water, acetone and dimethylformamide.

After immersing the CLS coating in this dye bath for 30 seconds, it isdried without washing, then exposed through a line image to a No. 2photoflood lamp for 10 seconds at a distance of 24 inches.

When the exposed CLS coating is immersed in a physical developer such asDeveloper 2 (composition of which is given in above Example 3) for oneminute at 20 C., a direct positive image is obtained with silverphysically developed in the unexposed areas while the light exposedareas remained relatively clear.

It will be apparent from all of the foregoing description and theexamples of the invention that any other of the sensitizing dyes definedin Formulas I to III and VIl to Xll above can be substituted into thepreceding examples in place of the specified dyes to given generallysimilar good quality direct positive images.

In the above examples, the images formed by physical development aresilver or palladium-silver. However, other metals are known for use inphysical development and can be used for the same purposes as silver bythe appropriate substitution of metallic salts. Metals which are membersof the electromotive scale below hydrogen are those which are mostcommonly employed for this purpose and include copper, mercury,platinum, gold, and the like. The use of these metals to form images iswithin the scope of this invention.

The invention has been described in detail with particular reference topreferred embodiments thereof, but it will be understood that variationsand modifications can be effected within the spirit and scope of theinvention.

We claim:

1. A non-silver halide direct positive photographic material comprisingnon-silver halide physically developable nuclei having adsorbed theretoan organic dye which is an electron acceptor.

2. A non-silver halide direct positive photographic material comprisingnon-silver halide physically developable nuclei having an averagediameter of up to about 0.5 micron, said nuclei having adsorbed theretoan organic dye which is an electron acceptor having an anodicpolarographic halfwave potential and a cathodic polarographic halfhalfwave potential which, when added together, give a positive sum. 7

3. A photographic material as defined in claim 2 wherein said nucleihave an average diameter of from 0.001 to 0.25 micron.

4. A non-silver halide direct positive photographic material 0comprising non-silver halide physically developable nuclei havingadsorbed thereto an electron accepting dye selected from the groupconsisting of (l) a methine dye containing a desensitizing nucleusselected from the group consisting of (a) a 5- to 6-membered nitrogencontaining heterocyclic nucleus of the type used in cyanine dyes havinga nitro group substituted on a carbon atom thereof (b) animidazo[4,5-b]quinoxaline nucleus and (c) a 2-arylindole nucleus; (2) abenzylidene dye comprising a ketomethylene nucleus of the type used inmerocyanine dyes joined by methine linkage to a nitro substituted arylgroup; (3) a cyanine dye having at least one methine group wherein thehydrogen atom thereof is replaced with a halogen atom selected from thegroup consisting of chlorine, bromine and iodine atoms; and (4) a dyeselected from the group consisting of a pyrylium dye, a thiapyryliumdye, and a selenapyrylium dye.

5. A non-silver halide direct positive photographic material comprisingnon-silver halide physically developable nuclei selected from the groupconsisting of silver, titanium and palladium nuclei, said nuclei havingadsorbed thereto an electron accepting dye selected from the groupconsisting of (l) a methine dye containing a desensitizing nucleusselected from the group consisting of (a) a 5- to 6-membered nitrogencontaining heterocyclic nucleus of the type used in cyanine dyes havinga nitro group substituent on a carbon atom thereof; (b) animidazo[4,5-b]quinoxaline nucleus and (c) a 2-arylindole nucleus; (2) abenzylidene dye comprising a ketomethylene nucleus of the type used inmerocyanine dyes joined by methine linkage to a nitro substituted arylgroup; (3) a cyanine dye having at least one methine group wherein thehydrogen atom thereof is replaced with a halogen atom selected from thegroup consisting of chlorine, bromine and 19 iodine atoms; and (4) a dyeselected from the group consisting of a pyrylium dye, a thiapyryliumdye, and a selenapyrylium dye.

6. A non-silver halide direct positive light sensitive photoof the typeused in merocyanine dyes, at least one of 2;, and Z and at least one of2 and Q being nitro-substituted.

7. A direct positive material in accordance with claim 6 wherein saidnuclei is selected from the group consisting of silver, titanium andpalladium nuclei.

8. A photographic element comprising a support having graphic materialcomprising non-silver halide physical 5 coated thereon a non-silverhalide direct positive photodevelopment sites of heavy metal nucleihaving an average graphic material comprising non-silver halidephysically particle diameter less than about 0.25 having adsorbedthereto developable nuclei having adsorbed thereto an organic dye a dyeselected from the group consisting of the reaction which is an electronacceptor. product of bromine and a monomethine cyanine dye salt, and 9.A photographic element comprising a support having a dye selected fromthose having one of the following formu- 10 coated thereon a non-silverhalide direct positive photo las: graphic material comprising non-silverhalide physically developable nuclei having adsorbed thereto an electronaccepting dye selected from the group consisting of l) a N N N N l 5methine dye containing a desensitizing nucleus selected from x the groupconsisting of (a) a 5- to o-membered nitrogen con- T tainingheterocyclic nucleus of the type used in cyanine dyes having a nitrogroup substituted on a carbon atom thereof; (b) animidazo[4,5-b1quinoxaline nucleus and (c) a 2-arylindole X nucleus; (2)a benzylidene dye comprising a ketomethylene R nucleus of the type usedin cyanine dyes joined by methine N linkage to a nitro substituted arylgroup; (3) a cyanine dye having at least one methine group wherein thehydrogen atom R -N(-CH=CH)g-l-C=L(-L=L)n C thereof is replaced with ahalogen atom selected from the group consisting of chlorine, bromine andiodine atoms; and N (4) a dye selected from the group consisting of apyrylium dye, R1 X a thiapyrylium dye and a selenapyrylium .dye. R 10. Adirect positive photographic material comprising 1 physicallydevelopable Carey Lea silver having adsorbed N thereto the electronaccepting dye 2,6-Bis(p-methoxyphenyl)- :0 T )34-(p-pentyloxyphenyl)thiapyrylium perchlorate.

11. A process for preparing a positive metallic image which N Ncomprises physically developing an imagewise exposed photographicelement comprising a support having coated thereon a non-silver halidedirect positive photographic material comprising non-silver halidephysically developable nuclei having L=L--((CH=C1I),, ,=1 I x adsorbedthereto an organic dye which is an electron acceptor. 12. A process forpreparing metallic images which comprises physically developing animagewise exposed photo- Rs graphic element comprising a non-silverhalide photographic t Rm 1 i (CH=CH) 1( 3=L L=L k ,-o (=CHCH) 1=l I-R1 X5 Ql, R I i(CH=CH)5-1=L-L=:0

material comprising non-silver halide physically developable K K nucleihaving adsorbed thereto an organic dye selected from ArL=( 3-C I=O thegroup consisting of l) a methine dye containing a desen- R sitizingnucleus selected from the group consisting of (a) a 5- to 6-memberednitrogen containing heterocyclic nucleus of the type used in cyaninedyes having a nitro group substituted on a carbon atom thereof; (b) animidazo[4,5-b1quinoxaline 6 nucleus; and (c) a 2-arylindole nucleus (2)a benzylidene dye A comprising a ketomethylene nucleus of the type usedin merowwfiq I g cyanine dyes joined by methine linkage to a nitrosubstituted wherein n represents a positive integer of from 1 to 4; dand k aryl group; (3) a cyanine dye having at least one methine eachrepresents a positive integer of from 1 to 3; g, h, j and p groupwherein the hydrogen atom thereof is replaced with a each represents apositive integer of from 1 to 2; L represents halogen atom selected fromthe group consisting of chlorine, a methine linkage; each R, R R R R R Rand R bromine and iodine atoms; and (4) a dye selected from therepresents a member independently selected from the group groupconsisting of a pyrylium dye, a thiapyrylium dye and a consisting of analkyl group, an alkenyl group and an aryl selenapyrylium dye. group; Arepresents an atom selected from the group consist- 13. A process asdefined in claim 12 wherein said nuclei is ing of oxygen, sulfur andselenium; R, R, and R each selected from the group consisting of silver,titanium and palrepresents a member selected from the group consistingof an ladium nuclei, and said physical development is conducted alkylgroup, an alkoxy group, an alkenyl group and an aryl with a compositioncomprising silver halide developing agent group; Ar represents an arylgroup; Ar represents a nitro suband silver halide solvent. stituted arylgroup; X, X X and X each represents an acid 14. The process of formingdirect positive images wherein anion; Z, Z Z Z and 2:, each representsthe non-metallic an imagewise exposed photographic element comprising aatoms required to complete a heterocyclic nucleus of the type supporthaving coated thereon physically developable Carey used in cyanine dyescontaining from 5 to 6 atoms in the Lea silver having adsorbed theretothe electron accepting dye heterocyclic ring; and Q, Q, and Q eachrepresents the non-2,6-Bis(p-methoxyphenyl)-4-(p-pentyloxyphenyl)thiapyrylimetallic atomsrequired to complete a ketomethylene nucleus u p c at is phy ically d pd with a Comp sition comprising silver chloride and sodium thiosulfate.

2. A non-silver halide direct positive photographic material comprisingnon-silver halide physically developable nuclei having an averagediameter of up to about 0.5 micron, said nuclei having adsorbed theretoan organic dye which is an electron acceptor having an anodicpolarographic halfwave potential and a cathodic polarographic halfhalfwave potential which, when added together, give a positive sum.
 3. Aphotographic material as defined in claim 2 wherein said nuclei have anaverage diameter of from 0.001 to 0.25 micron.
 4. A non-silver halidedirect positive photographic material comprising non-silver halidephysically developable nuclei having adsorbed thereto an electronaccepting dye selected from the group consisting of (1) a methine dyecontaining a desensitizing nucleus selected from the group consisting of(a) a 5- to 6-membered nitrogen containing heterocycliC nucleus of thetype used in cyanine dyes having a nitro group substituted on a carbonatom thereof (b) an imidazo(4,5-b)quinoxaline nucleus and (c) a2-arylindole nucleus; (2) a benzylidene dye comprising a ketomethylenenucleus of the type used in merocyanine dyes joined by methine linkageto a nitro substituted aryl group; (3) a cyanine dye having at least onemethine group wherein the hydrogen atom thereof is replaced with ahalogen atom selected from the group consisting of chlorine, bromine andiodine atoms; and (4) a dye selected from the group consisting of apyrylium dye, a thiapyrylium dye, and a selenapyrylium dye.
 5. Anon-silver halide direct positive photographic material comprisingnon-silver halide physically developable nuclei selected from the groupconsisting of silver, titanium and palladium nuclei, said nuclei havingadsorbed thereto an electron accepting dye selected from the groupconsisting of (1) a methine dye containing a desensitizing nucleusselected from the group consisting of (a) a 5- to 6-membered nitrogencontaining heterocyclic nucleus of the type used in cyanine dyes havinga nitro group substituent on a carbon atom thereof; (b) animidazo(4,5-b)quinoxaline nucleus and (c) a 2-arylindole nucleus; (2) abenzylidene dye comprising a ketomethylene nucleus of the type used inmerocyanine dyes joined by methine linkage to a nitro substituted arylgroup; (3) a cyanine dye having at least one methine group wherein thehydrogen atom thereof is replaced with a halogen atom selected from thegroup consisting of chlorine, bromine and iodine atoms; and (4) a dyeselected from the group consisting of a pyrylium dye, a thiapyryliumdye, and a selenapyrylium dye.
 6. A non-silver halide direct positivelight sensitive photographic material comprising non-silver halidephysical development sites of heavy metal nuclei having an averageparticle diameter less than about 0.25 having adsorbed thereto a dyeselected from the group consisting of the reaction product of bromineand a monomethine cyanine dye salt, and a dye selected from those havingone of the following formulas:
 7. A direct positive material inaccordance with claim 6 wherein said nuclei is selected from the groupconsisting of silver, titanium and palladium nuclei.
 8. A photographicelement comprising a support having coated thereon a non-silver halidedirect positive photographic material comprising non-silver halidephysically developable nuclei having adsorbed thereto an organic dyeWhich is an electron acceptor.
 9. A photographic element comprising asupport having coated thereon a non-silver halide direct positivephotographic material comprising non-silver halide physicallydevelopable nuclei having adsorbed thereto an electron accepting dyeselected from the group consisting of (1) a methine dye containing adesensitizing nucleus selected from the group consisting of (a) a 5- to6-membered nitrogen containing heterocyclic nucleus of the type used incyanine dyes having a nitro group substituted on a carbon atom thereof;(b) an imidazo(4,5-b)quinoxaline nucleus and (c) a 2-arylindole nucleus;(2) a benzylidene dye comprising a ketomethylene nucleus of the typeused in cyanine dyes joined by methine linkage to a nitro substitutedaryl group; (3) a cyanine dye having at least one methine group whereinthe hydrogen atom thereof is replaced with a halogen atom selected fromthe group consisting of chlorine, bromine and iodine atoms; and (4) adye selected from the group consisting of a pyrylium dye, a thiapyryliumdye and a selenapyrylium dye.
 10. A direct positive photographicmaterial comprising physically developable Carey Lea silver havingadsorbed thereto the electron accepting dye2,6-Bis(p-methoxyphenyl)-4-(p-pentyloxyphenyl)thiapyrylium perchlorate.11. A process for preparing a positive metallic image which comprisesphysically developing an imagewise exposed photographic elementcomprising a support having coated thereon a non-silver halide directpositive photographic material comprising non-silver halide physicallydevelopable nuclei having adsorbed thereto an organic dye which is anelectron acceptor.
 12. A process for preparing metallic images whichcomprises physically developing an imagewise exposed photographicelement comprising a non-silver halide photographic material comprisingnon-silver halide physically developable nuclei having adsorbed theretoan organic dye selected from the group consisting of (1) a methine dyecontaining a desensitizing nucleus selected from the group consisting of(a) a 5- to 6-membered nitrogen containing heterocyclic nucleus of thetype used in cyanine dyes having a nitro group substituted on a carbonatom thereof; (b) an imidazo(4,5-b)quinoxaline nucleus; and (c) a2-arylindole nucleus (2) a benzylidene dye comprising a ketomethylenenucleus of the type used in merocyanine dyes joined by methine linkageto a nitro substituted aryl group; (3) a cyanine dye having at least onemethine group wherein the hydrogen atom thereof is replaced with ahalogen atom selected from the group consisting of chlorine, bromine andiodine atoms; and (4) a dye selected from the group consisting of apyrylium dye, a thiapyrylium dye and a selenapyrylium dye.
 13. A processas defined in claim 12 wherein said nuclei is selected from the groupconsisting of silver, titanium and palladium nuclei, and said physicaldevelopment is conducted with a composition comprising silver halidedeveloping agent and silver halide solvent.
 14. The process of formingdirect positive images wherein an imagewise exposed photographic elementcomprising a support having coated thereon physically developable CareyLea silver having adsorbed thereto the electron accepting dye2,6-Bis(p-methoxyphenyl)-4-(p-pentyloxyphenyl)thiapyrylium perchlorateis physically developed with a composition comprising silver chlorideand sodium thiosulfate.